Nightopian Collection
If you complete Christmas NiGHTS as both Elliot and Claris, you will unlock the option to view the Nightopian Collection on the main menu. This will show the Nightopians, Mepians, Nightopian/Mepian eggs in each level, as well as the mood of the Nightopians and Mepians in that level (the music alters based on how happy or sad they are).